1. Field of the Invention
The present invention relates to a cutting tool for drilling and turning. The tool includes a base body having at least one coolant bore, as well as a clamping part and an essentially cylindrically formed working part following the clamping part in an axial direction. An indexable tip, which is releasably connected to the working part at its end opposite the clamping part, includes, in plan view, circumferential cutting edges. The working part has a flute running in the direction of the tool axis and a form-locking seat for the indexable tip with cutting edges slightly projecting.
Further, the invention relates to an indexable tip for a cutting tool for machining materials, in particular metals and alloys. The indexable tip is limited by a flat supporting area, a face opposite the supporting area and open spaces connecting the supporting area and the face. Also, an attachment device mounting can be optionally embodied as a center hole, whereby, in the plan view of the indexable tip, six cutting edges run circumferentially.
2. Discussion of Background Information
Cutting tools of the specified type, which can be used for different machinings, have an extraordinarily high technical and economic importance for the manufacture of work pieces, particularly those made of metal, in plant and machine construction. In a relatively short time, such cutting tools render possible the manufacture of a large number of work pieces, particularly those with complex geometric shapes, and can essentially ensure adequate dimensional accuracy and surface quality thereby. When several machining operations are performed with a single cutting tool, the machining time can be kept short, because expensive changeover times for exchanging cutting tools do not apply. In addition, with a computer-controlled machining of parts, the programming effort can be substantially reduced.
To meet the requirement for economic efficiency for tools, the achievement of as long a tool life as possible in practical use is required. For this reason, with cutting tools of the type mentioned at the outset, cutting attachments made of sintered materials featuring circumferential cutting edges are used. The wear on the cutting edges or their length of use is influenced by several factors, e.g., a distribution of forces in the tip when in contact with the usually rotating work piece and/or the transfer of force from the tip to the base body.
In the production of work pieces of the highest quality, an appropriately ensured stability and a low tendency of the tool to vibrate with simultaneously good cutting action are necessary.
In order to further achieve the highest cost-effectiveness and surface quality, the cutting tools of the type mentioned at the outset should permit a variety of possible methods for machining work pieces, as well as feature the lowest possible tool wear, even in high capacity operation, and at the same time ensure a desired dimensional accuracy of the machined surfaces. However, the realization of such a combination of requirements is difficult to achieve.
In the published patent application DE 2733705, a cutting tool equipped with an indexable tip is described that is suitable for drilling and turning and whose indexable tip features four usable cutting edges. Two cutting edges each are located on the upper side and the underside of an indexable tip that is approximately rhomboid in plan view. The indexable tip is shaped such that a change of cutting edges occurs by turning, although the supporting area of the tip is reduced, by which the stability and thus also the surface quality achieved can be substantially impaired.
In EP 0642859 B1 another cutting tool for drilling into the solid and turning is suggested. The cutting tool includes essentially a base body and an indexable tip that is rhomboid in plan view, featuring alternately obtuse and acute angles, with four cutting edges rounded off at the corners and located on the upper side, whereby the tip is connected to the base body such that the front cutting edge in plan view runs vertically to the tool axis of rotation, does not deviate from the vertical more than a maximum of about 0.5°, and does not extend more than about 10% beyond the tool axis of rotation at the transition to the corner rounding. It is further provided that in the front view of the tool, the cutting edge intersects the drill longitudinal axis or features a maximum spacing of about 2% of the drill diameter. Such a cutting tool should feature improved stability and render possible a more even bore base in pocket bores. However, it can be considered detrimental for the tool that can be favorably used for drilling, that with turning and, in particular, an inside turning and die sinking with larger dimensions the largest chip width is limited to half the diameter of the machining section of the tool. Further, after a single turn of the indexable tip, this must be replaced for cutting edge wear and for cutting edge renewal.
The known cutting tools for drilling into the solid and for turning have the disadvantage in common, that the only machining widths to be achieved with them correspond essentially to the length of the face cutting edge and thus half the diameter of the machining part of the tool. Although a drilling outside the center optionally allows a slight increase of the bore diameter, this is limited to about 10% of the same. Experience has shown in operation that variable bore diameters even beyond this size are required, which, however, can only be achieved through the use of several different cutting tools or through an expensive machining technology. This is linked to a considerable loss of working time.
In addition, the cutting tools known from prior art are designed such that in plan view the indexable tip is mounted almost completely on one side of the base body or machining part of the tool between the surface and the axis of rotation. The uneven distribution of forces thus caused can result in vibrations and stability problems, through which the tool life of the four cutting edges is reduced, and the surface and work piece quality are adversely affected. It has also been shown that with cutting tools with cutting edges located on the upper side, because of the approximately square shapes of such indexable tips, an incorrect orientation of the same in the tip seat and a subsequent defective attachment can easily occur, particularly if tool users are under pressure, and thus hectic work methods and carelessness often result. Although attempts are made to prevent defective attachment and the consequent dangers for user and tool by additionally attaching signs on such indexable tips, such dangers cannot be ruled out.